1. Field of the Invention
The invention relates to the use of lasers on small firearms to permit a combined sighting and range finder capability.
2. Description of the Related Art
It is well known that even skilled marksman with a handgun have been unable to hit a target as close as 7 meters when attempting to draw the weapon and fire at speed. In target shooting, the shooter must obtaining the proper stance by carefully positioning the feet and the "free" hand to find the most stable condition, producing no muscular strain that will adversely effect the accuracy of the shot. Most importantly, the shooter must be able to obtain an identical position each time the weapon is fired to achieve the greatest accuracy. As the whole upper torso moves during each breath, breath control plays a vital role in the process. Since there can be no body movement at the time the trigger is fired, obviously the act of breathing must be stopped during the time the weapon is aimed and fired.
Sight picture and aim are critical if the shooter is to fire the most accurate shot or series of shots. When a mechanical pistol sight is properly aligned, the top of the front sight should be level with the top of the rear sight, with an equal amount of light on either side of the front sight. Using this sight picture requires that the shooter focus his shooting eye so that the sights are in focus and the target is out of focus. Added to the difficulty, the trigger, all of the above must be maintained while the trigger is released using direct, even pressure to keep the barrel of the gun pointing at the target. These skills require tremendous practice, with each shot fired needing the utmost concentration if the shooter is to obtain maximum accuracy.
It is clear that the recommended methods of achieving maximum shooting accuracy useful for target shooting, must be severely modified when a handgun is used in a law enforcement situation. While the degree of accuracy necessary for target shooting and the distances and substantial lower, accuracy is still vital. Law enforcement official are instructed to fire only as a last resort, cognizant of the fact that their intended target will mostly be killed. Shooting to wound occurs only in the movies. Law enforcement officers typically use higher caliber handguns, mostly 9 mm, which are designed to immobilize with a single shot if that shot strikes a vital area. Given the inherent inaccuracies in the shooting process itself, exacerbated by the stress and fear of the police officer in what may be a life threatening situation for him/her, the exact location of the bullet where millimeters can mean the difference between death and survival cannot be known a priori by the even the most skilled marksman.
Mechanical sights have limited value in many situation where an officer must quickly draw his gun, perhaps while moving, and fire at a close target without sufficient time to properly obtain a sight picture. Under these circumstances, instinctive aiming, that is, not using the sights but rather "feeling where the gun barrel is pointing using the positioning of the hand holding the gun, is the preferred method. While this method, akin to the typical television cowboy shootouts, can be reasonably effective at short distances, obviously large errors in aiming are easily introduced, especially when the officer must frequently fire his/her weapon from a different hand position that has been used for practice. For example, bullet proof shields are used to protect the officer from being fired upon such as in a riot situation. In those circumstance, the officer must reach around his/her shield or other barricade and instinctively aim and fire his/her gun with the handgun in a very different orientation that would be experience if fired from a standing, drawn from a holster position. Small changes in barrel orientation due to the sight radius of the typical law enforcement handgun can produce substantial errors relative to the target. Accurate instinctive shooting is not considered practical beyond 20 feet for the average shooter.
The same problems face a soldier in a combat situation. While a rifle is inherently more accurate that a handgun, the stress of combat, the need to fire rapidly but accurately in order to survive is sufficient to introduce substantial errors into the sighting process. These problems are further exacerbated by the fact that most military personnel do not have sufficient practice time with their weapon to develop a high proficiency, particular in combat simulated situations.
An additional problem encountered in the military situation is the need for a sighting system that can be easily moved from one weapon to another. As warfare increases in sophistication, the need for more versatile armament increases correspondingly. Ideally, an operator should be able to quickly and confidently move the sighting system from one weapon to another without needing any field adjustments.
Laser technology has been previously introduced as a solution to the problem of accurately and rapidly sighting a handgun on an intended target. The typical laser sight is mounted on the top on the handgun or on the bottom. The laser sight when properly aligned, places a red light dot on the target where the bullet will strike if the gun is fired. Using this type of sight, enables the law officer to rapidly instinctively properly position the weapon and be certain of his/her intended target. Using a laser sight enables accurate shots to be fired at distances of more than 50 feet, sufficient for most combat law enforcement situations requiring the use of handguns.
Laser sights have proved their worth for sighting weapons having substantially flat trajectories over extended distances such as the M-16 or for powerful handguns having a relatively fiat trajectory over a short effective firing distance such as 9 mm. However, the usefulness for laser sights is substantially diminished when used with weapons that launch a projectile having a large and highly variable trajectory over the effective firing range of weapon, for example, the mortar. The mortar is in essence a muzzle loading cannon that fire shells at low velocities, comparatively short ranges, and at a substantial angular elevation due to the large trajectory of the projectile. The mortar is typically "sighted in" by guessimating the distance to the target, then adjusting the angular elevation after each fired round impacts by "guessimating" the distance from the target, until the weapon is finally adjusted so that the fired shell will hit the target. A similar situation is present when attempting to fire a grenade launcher. This procedure is wasteful of ammunition, time consuming providing the enemy with sufficient time to respond or retreat. It is well known that the error rate of 20% is considered the norm when firing such weapons.
Laser range finding units have been proposed to provide an accurate means for measuring distance from one location to another. One proposed solution is U.S. Pat. No. 3,464,770, issued to Schmidt on Sep. 2, 1969, discloses a combined sighting mechanism and laser range finder. In this invention, a laser sends a beam to the target which must be reflected back to a receiver through an elaborate mirror/lens arrangement. The distance to the device is measured by measuring the time interval between emission and reception. Such a device is not practical for installation on a small arm field weapon due to the extraordinary cost of manufacturing and the delicate nature of necessary optics and electronics.
Another invention representative of this genre is U.S. Pat. No. 4,690,550, issued to Kuhne on Sep. 1, 1987, which discloses a laser range finder that has a common telescope for transmitting and receiving the laser signal. Again, the distance to the target is determined by measuring the time interval between emission and reception.
While these devices as well as the numerous others that exist using that principle will accurately and rapidly permit the determination of the distance to a target, the prior art does not disclose a laser range finding apparatus that is suitable for use with a grenade launcher attached to a rifle or other small arms such as the mortar.